Add 'Replying to' TextView to statuses

With recent changes to Soapbox replies from instances that use that FE no longer contain mentions in Status content which may look confusing for non-Soapbox users. I added a CustomTextView that would display mentioned user and (if there were more users in that discussion) number of users in that discussion. Clicking on an @ of a user will redirect to said user's profile. Clicking on any other part of the CustomTextView will invoke a separate activity with list of mentioned users.